llvm dev - Sep 2015 - Testing "normal" cross-compilers versus GPU backends

>>> The Hexagon precedent is interesting; Krzysztof said they set the
default
>>> triple, and didn't have to xfail all that much stuff. 
Searching the tree,
>>> I find exactly 7 individual tests marked XFAIL: hexagon, plus it
disables
>>> all of ExecutionEngine, and turns off the 'object-emission'
feature.
>>> 
>>> I'm curious if you would try setting the default triple to
match your
>>> target, and see what /kinds/ of tests fail.  The raw number is much
less
>>> interesting than in the categories.
>> 
>> Failing tests attached, let me know which ones you’d like me to
investigate.
> 
> Tests:
> <failing_tests>
> 
> (note I forced enable the “native” feature on this run)
So, just looking at the first one in that list for an example, running:
llc -mtriple amdgcn test/CodeGen/Generic/2002-04-14-UnexpectedUnsignedType.ll
you get an error of:
error: unsupported call to function bar in foo

...because apparently AMDGPU simply doesn't support function calls. At all.

That is a rather unusual feature to be missing, and I'd imagine is causing a
fair number of the other nominally-generic tests to fail too...

> -----Original Message-----
> From: James Y Knight [mailto:jyknight at google.com]
> Sent: Friday, September 04, 2015 10:12 AM
> To: Mehdi Amini; Mehdi Amini via llvm-dev
> Cc: Robinson, Paul
> Subject: Re: [llvm-dev] Testing "normal" cross-compilers versus
GPU
> backends
> 
> >>> The Hexagon precedent is interesting; Krzysztof said they set
the
> default
> >>> triple, and didn't have to xfail all that much stuff. 
Searching the
> tree,
> >>> I find exactly 7 individual tests marked XFAIL: hexagon, plus
it
> disables
> >>> all of ExecutionEngine, and turns off the
'object-emission' feature.
> >>>
> >>> I'm curious if you would try setting the default triple to
match your
> >>> target, and see what /kinds/ of tests fail.  The raw number is
much
> less
> >>> interesting than in the categories.
> >>
> >> Failing tests attached, let me know which ones you’d like me to
> investigate.
> >
> > Tests:
> > <failing_tests>
> >
> > (note I forced enable the “native” feature on this run)
> 
> So, just looking at the first one in that list for an example, running:
> llc -mtriple amdgcn test/CodeGen/Generic/2002-04-14-
> UnexpectedUnsignedType.ll
> you get an error of:
> error: unsupported call to function bar in foo
> 
> ..because apparently AMDGPU simply doesn't support function calls. At
all.
> 
> That is a rather unusual feature to be missing, and I'd imagine is
causing
> a fair number of the other nominally-generic tests to fail too...
Hmm I'm told GPUs as a class typically don't support calls (everything
has
to be inlined).

Perhaps the more appropriate direction here is to invent a "gpu"
config flag
and mark some things XFAIL: gpu.
--paulr

On 09/04/2015 10:25 AM, Robinson, Paul via llvm-dev
wrote:
>
>> -----Original Message-----
>> From: James Y Knight [mailto:jyknight at google.com]
>> Sent: Friday, September 04, 2015 10:12 AM
>> To: Mehdi Amini; Mehdi Amini via llvm-dev
>> Cc: Robinson, Paul
>> Subject: Re: [llvm-dev] Testing "normal" cross-compilers
versus GPU
>> backends
>>
>>>>> The Hexagon precedent is interesting; Krzysztof said they
set the
>> default
>>>>> triple, and didn't have to xfail all that much stuff. 
Searching the
>> tree,
>>>>> I find exactly 7 individual tests marked XFAIL: hexagon,
plus it
>> disables
>>>>> all of ExecutionEngine, and turns off the
'object-emission' feature.
>>>>>
>>>>> I'm curious if you would try setting the default triple
to match your
>>>>> target, and see what /kinds/ of tests fail.  The raw number
is much
>> less
>>>>> interesting than in the categories.
>>>> Failing tests attached, let me know which ones you’d like me to
>> investigate.
>>> Tests:
>>> <failing_tests>
>>>
>>> (note I forced enable the “native” feature on this run)
>> So, just looking at the first one in that list for an example, running:
>> llc -mtriple amdgcn test/CodeGen/Generic/2002-04-14-
>> UnexpectedUnsignedType.ll
>> you get an error of:
>> error: unsupported call to function bar in foo
>>
>> ..because apparently AMDGPU simply doesn't support function calls.
At all.
>>
>> That is a rather unusual feature to be missing, and I'd imagine is
causing
>> a fair number of the other nominally-generic tests to fail too...
> Hmm I'm told GPUs as a class typically don't support calls
(everything has
> to be inlined).
>
> Perhaps the more appropriate direction here is to invent a "gpu"
config flag
> and mark some things XFAIL: gpu.
> --paulr
Mehdi - Could you list a couple of the features that show up in generic 
tests which your target doesn't support by design?  After reading 
through the discussion to this point, I don't really have a feel for 
that.   Additionally, do you have any sense for how common that set is 
across GPU targets?

Paul - If we introduce the type of flag your talking about, we should 
probably have a discussion about which classes of backends LLVM supports 
and try to create a *documented* list of feature expectations somewhere.

p.s. Maybe I missed something, but why did simply using "XFAIL:
AMDGPU"
get rejected?  That seems like the easiest fix.

Philip